Tensiometer

ABSTRACT

Mechanism for determining and varying the tension present in a rod being rolled as it passes between adjacent stands in a rod mill. The read-out gives an indication enabling the operator to make manual speed adjustment of the rolls to change the rod tension to the desired norm, or through a feed-back device the roll speeds may be changed automatically to achieve the same result. The mechanism operates on the principle of temporarily applying a transverse force moved through a fixed distance against the moving rod. The resistance to this force measured by a load cell and associated meters will give an indication of the then existing rod tension as it moves between adjacent roll stands and an indication of the adjustment to be made in roll speeds to change the rod tension to the desired norm.

United States Patent 1 Wykes I [111 3,744,288 [451 July 10, 1973 TENSIOMETER Robert D. Wykes, Worcester, Mass.

[73] Assignee: Morgan Construction Company,

Worcester, Mass.

22 Filed: Dec.22,1971

21 Appl. No.: 210,852

[75] Inventor:

[52] U.S. Cl. 72/17, 72/205 [51] Int. Cl B21b 37/04 [58] Field of Search 72/17, 9, l0, 11, 72/12, 32, 205

[56] References Cited UNITED STATES PATENTS 3,169,420 2/1965 Stone et al 72/205 X 3,188,841 6/1965 Wallace 72/9 2,345,765 4/1944 Michel 72/205 3,334,502 8/1967 Heindel et a1. 72/9 3,581,536 6/1971 Terwilliger.... 72/17 X 3,169,422 2/1965 Sims et al. 72/17 Primary Examiner-Milton S. Mehr AttorneyC. Yardley Chittick, Maurice E. Gauthier et al.

[57] ABSTRACT Mechanism for determining and varying the tension present in a rod being rolled as it passes between adjacent stands in a rod mill. The read-out gives an indication enabling the operator to make manual speed adjustment of the rolls to change the rod tension to the desired norm, or through a feed-back device the roll speeds may be changed automatically to achieve the same result. The mechanism operates on the principle of temporarily applying a transverse force moved through a fixed distance against the moving rod. The resistance to this force measured by a load cell and associated meters will give an indication of the then existing rod tension as it moves between adjacent roll stands and an indication of the adjustment to be made in roll speeds to change the rod tension to the desired norm.

7 Claims, 3 Drawing Figures PATENTEDJUL 1 0197s SHEET 2 0F 2 TENSIOMETER BACKGROUND OF THE INVENTION In the roughing stands of a continuous cast'copper rod mill, the presence of tension in the stock can have a pronounced harmful effect on the quality of the tinished product. This is because the structure of the stock passing through the roughing mill still has the coarse crystalline structure which is developed during the casting and cooling process. Further rolling refines the stock into a more fibrous structure less prone to damage due to tension.

Damage in the roughing mill takes the form of tensile cracks or ruptures which becomes elongated through subsequent rolling into seams and other defects. These defects continue in the stock throughout the rolling and show up in the finished rod making it unsuitable for drawing into small wire sizes.

One source of stock tension is a slight mismatch in the roll speeds of adjacent stands. If the mill is to operate without undesirable tension in the rod between stands, the speed ratios between stands must correspond inversely to the progressively diminishing crosssectional areas of the rod as it passes through the mill. In a continuous casting rolling mill, whether for nonferrous or ferrous material, small variations occur in the size and temperature of the cast section that is delivered to the first stand. Such variations influence the rolling characteristics in the roughing stands and tend to upset the rolling balance between stands.

In order to maintain a constant unit volume flow through a mill, the velocity of the stock leaving each stand times the cross-sectional area at the point must equal the velocity of the stock leaving all subsequent stands times the cross-sectional areas at those stands. To meet this requirements, roll stand speeds must be carefully set. If, for example, the rolls of the second stand are running a little too slowly so that they are not receiving the rod quite as fast as it is being delivered by the first stand, then the rod between the first and second stands will sag or buckle. On the other hand, if the rolls of the second stand are running a little too fast and delivering a volume of rod slightly greater than that being delivered by the first stand, then tension will develop in the rod. Therefore, it is of the utmost importance that the roll speeds of all stands be adjusted to accept rod from the preceding stand at the exact rate of delivery thereby avoiding saging of the rod in the one case, or placing it under undesirable tension in the other.

Once the speeds of the rolls have been properly adjusted, a mill can usually run for a substantial time before the development of unsatisfactory tension conditions in the rod between adjacent stands. However, periodic checking of the condition of the rod between stands should be made so that if undesirable tension conditions have developed, adjustments in the roll speeds can forthwith be made. Making such adjustments is difficult in present installations, particularly when the mill is enclosed to maintain a non-oxidizing atmosphere. To make adjustments under such conditions, it is necessary to open the mill'doors and adjust the rolls until the stock is running visibly slack, and then to readjust the rolls to get rid of the slackness without creating undesirable tension. The operator has to decide what degree of tension is proper and thereafter try to maintain this condition. Furthermore, be-

cause of the coolant spray present upon opening of the mill doors, and because it is easy to cause a cobble if too much slackness is inadvertendly produced, the operators frequently do not bother to adjust mill tension at all.

Accordingly, the present invention is designed to give a reading on suitable visible instruments exterior of the mill which will tell the operator to what extent the tension (or slackness) in the rod between adjacent stands differs from the desired norm. With this information available, the operator may then successively adjust the speeds of the rolls in the different stands so that the rod passes through the mill with the correct tension present in the rod between each pair of stands.

The invention also contemplates the inclusion of feedback mechanism which will cause automatic adjustment of the rolls upon each application of the testing procedure.

SUMMARY OF THE INVENTION The invention may be referred to as a tensiometer and consists of a plurality of indicating units with one unit functioning between each pair of adjacent stands. Thus, if there were four stands in the mill, three units would be needed to give the tension indications required. Each unit comprises transverse force applying means preferably in the form of a roller located just below the stock line about half way between the roll housings. The roller is attached to one arm of a bell crank which can be raised and lowered by means of an air or hydraulic actuated cylinder and piston or any other suitable mechanism. Between the cylinder piston rod and the other arm of the bell crank is located a socalled load cell, or any other suitable device for giving strain indications.

Energizing the cylinder causes the roller to be raised into contact with the stock as it is passing from one stand to the next. The roller is raised on each testing operation to a prescribed height above the normal center line of the stock and in this position the force exerted on the roller by the deflected rod may be converted through the included load cell to give an indication of the tension existing in this part of the moving rod. When the deflecting force is removed, the tension in the then deflected rod will be slightly less. That is to say, whatever the degree of original tension in the undeflected rod, the tension will be somewhat greater when the roller of the tensiometer has been moved to testing position.

The strain gauges in the load cell customarily function as a wheatstone bridge in an electrical circuit. A force application applied to the load cell causes a bridge imbalance which results in a potential difference proportional to the level of the applied force. The resulting change in current when amplified produces a usable signal.

The simplest use of this signal in the case of the tensiometer would be to provide on a gauge an indication of the force applied by the moving stock to the roller which advice can be used by the operator to make adjustment of the roll speeds. Additionally, the indication from the force applied could be used to actuate a feedback system to achieve automatic speed adjustment of I the rolls.

A load cell suitable for use in the present disclosure is that made by W. C. Dillon & Co., Inc., 1462 Keswick St., Van Nuys, Calif, and known as DILLON RE- MOTE INDICATING ELECTRONIC LOAD CELL SYSTEM.

With three tensiometers operating between four consecutive stands (which is a typical application), the operation would be as follows:

1. The initial setting would be made by first actuating the tensiometer to shift the roller against the moving rod thereby to hold the rod in deflected position. Then the stock tension in the deflected rod would be reduced by appropriate varying of the roll speeds until the tensiometer readout needle became unstable, indicating that the stock was on the point of buckling. Roll speeds would be adjusted to increase the tension until the needle became steady. This steady gauge reading would be considered the norm for this section of rod.

2. The tensiometer readings obtained in this manner between all pairs of stands would be noted.

3. Thereafter, when a check of mill tension was required, the tensiometers would be applied and roll speeds adjusted until the previously determined normal readings were obtained.

4. The tensiometers would be lowered clear of the stock after each check had been made.

In the second application designed to make automatic adjustment of roll speeds, the tensiometers would be timed to be applied automatically at suitable intervals. The resulting error signal would be used to instruct the motor speed controller to make the appropriate speed correction. When the tensiometer signals agreed with predetermined normal values, the tensiometer would be lowered'to inoperative position. As a quality control aid, the tensiometer signals could be recorded' for a later correlation with rod inspection records.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic showing of the invention in which there are three tensiometers each located between adjacent stands in a four-stand mill.

FIG. 2 is an enlarged elevation of one of the actuating units with the roller arm in a down inoperative position.

FIG. 3 is an enlarged elevation similar to FIG. 2 showing the roller engaging the rod after having moved through the prescribed distance to cause rod deflection.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, there is shown schematically a four-stand rolling mill with the horizontal rolls of the first stand indicated at 2 and 3, the vertical rolls of the second stand indicated at 4, the horizontal rolls of the third stand indicated at 6 and 7, and the vertical rolls of the fourth stand indicated at 8. The stock being rolled is indicated generally at 10 and its normal rolling position between successive stands is indicated at l2, l4 and 16. The stock feeding into the rolls 2 and 3 is ordinarily in billet form and the rolled rod on leaving the rolls 8 of the fourth stand will have been reduced in cross-sectional area to the size desired. The horizontal distance between the rolls of the several stands in a typical installation may be in the order of 4 feet, so that when the rod is passing through the mill under proper adjustment for tension between the stands, there will be little if any sagging of the rod below the normal center line positions at l2, l4 and l6.

Between each pair of roll stands are fluid actuated cylinders shown at 18, 20 and 22. These cylinders are mounted on any suitable fixed structure as at 24, 26 and 28. The fluid cylinder 18, illustrative also of cylinders 20 and 22, is shown in more detail in FIGS. 2 and 3. The cylinder has therein a piston 30 from which extends a piston rod 32. Fluid supply lines 34 and 36 under suitable valve control, alternately supply fluid to cause the piston 30 to move through a fixed stroke from one end of the cylinder to the other. Piston 32 is connected at 40 to the load cell 38 of a tensiometer. The other end of the load cell 38 is pivotally connected at 42 to the arm 44 of a bell crank 46 pivoted on fixed structure at 48. The other arm 50 of bell crank 46 has mounted on its end a grooved roller 52 pivoted for free rotation at 54.

With piston 30 in its down position as shown in FIG. 2, the roller 52 will be located and free of engagement with the moving stock or rod 10 as it advances from the horizontal rolls 2 and 3 to the vertical rolls 4 of the second roll stand.

When fluid is supplied to the cylinder 18 through pipe 36, the piston 30 is moved from its down position in FIG. 2 to the up position shown in FIG. 3 placing the load cell 38 in tension. Fluid in the upper part of the cylinder is exhausted through pipe 34. This up movement of the piston is for a predetermined distance. The

bell crank 46 is rotated clockwise through a constant angle on each occasion of piston operation and causes the roller 52 to move transversely of the rod 10 to first engage the rod and then to lift it for a fixed distance at a localized position approximately midway between the roll stands as shown in FIG. 3. Obviously, when the rod 10 is deflected to the position shown in FIG. 3, the tension in the rod between the first and second stands will be increased and there will be a force against roller 52 directly related to the tension existing in rod 10 prior to its deflection by roller 52. Alternatively, the lever system for actuating the force applying means could be altered to place the load cell 38 in compression without changing the movement of roller 52 against the rod 10. The force of the deflected rod 10 against roller 52, whatever it may be, will be indicated on the tensiometer gauge 56 actuated by the tension (or compression, as the case may be) then existing in the load cell 38.

By suitable preliminary experimentation in which the rolls 2, 3 and 4 are set at speeds to produce different degrees of tension in the rod 10 while running freely between the first and second stands, then a corresponding series of increased tensions will be developed when the roller 52 is raised to deflect rod 10 to the position shown in FIG. 3. These tensions of the deflected rod will be indicated as forces on the gauge 56 through the operation of load cell 38. Thus, the force readings on gauge 56 when the rod is deflected will give an indirect indication of the tension in rod 10 when running freely as in FIG. 2 prior to application of the tensiometer. The gauge information may then be translated into an increase or decrease in the rotational speeds of rolls 2, 3 and/or 4 to bring the tension of the rod between the first and second stands with the tensiometer in operative condition to the predetermined desired normal tension.

Having made the ad jistment to correct the tension of the rod between the first and second stands, then the second cylinder 20 and its related tensiometer is brought into operation to give an indication of the then existing tension in section 14 of the rod as it passes freely between the second and third stands. With the indication then appearing in gauge 56, the speeds of rolls 6 and 7 may be adjusted to bring the tension of section 14 of the rod to the desired norm. Then the tensiometer controlled by cylinder 22 is brought into operation in the same manner in which cylinders 18 and 20 were actuated and a third tensiometer reading will be obtained on gauge 56 indicating the tension conditions existing in freely running undeflected section 16 of rod 10. Adjustments of the speed of rolls 8 may then be made to bring the tension of section 16 to the desired norm.

The collective corrections made as aforesaid to the roll speeds will then result in the rod 10 passing through the mill under proper tension conditions at all three sections 12, 14 and 16. By so doing, the deleterious cracks that develop when the rod is under too great a tension will be eliminated and the tendency to cobble when the rod is too slack between stands will be elimi nated.

Referring again to FIG. 1, it will be noted that there are three circuits 58, 60 and 62 running from the load cells 38, 38' and 38" to the tensiometer gauge 56. There are also three switches numbered A, B and C on the panel of gauge 56. These switches when actuated control corresponding solenoid valves 18', and 22' which cause appropriate operation of the pistons in cylinders 18, 20 and 22, respectively, to raise the related rollers 52 through their fixed limits of travel to create, through rod deflection, the increased tension in the respective sections of rod 12, 14 and 16 whereby the reading of the force created by such increased tension can predictably determine the pre-existing tension in the rod when running free. Also, on the panel 56 will be noted the load cell selector switch 64 which shifts the circuits from load cell 38 of cylinder 18 to load cell 38 of cylinder 20 to load cell 38" of cylinder 22 as the operator may select.

In summary, the operating procedure of the aforesaid mechanism is as follows:

I. Apply all tensiometers in prompt succession (or simultaneously if separate gauges are available) to the moving rod sections.

2. Obtain and note the readout of the tensiometers.

3. Adjust the roll drive speeds to obtain the required load values of the tensiometers to produce the required normal tension between stands.

4. Recheck the tensiometer load values after each adjustment.

5. When all readings are correct, retract all tensiometers and switch off the system.

6. Repeat the above procedure at about minute intervals or when desired, either manually or auto-' matically.

The invention as claimed is intended to encompass all types of rolling mills, ferrous or non-ferrous, regardless of the type of billet supply means. its preferred use has been in the rolling of non-ferrous rod fed by a continuous casting wheel.

It is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of the disclosure which do not constitute departures from the spirit and scope of the invention.

1 claim:

1. The method of adjusting the tension of moving stock being rolled in a rolling mill to a predetermined normal tension between each pair of adjacent stands comprising the steps of:

transversely moving the stock at a position intermediate the said adjacent roll stands a standard fixed distance by the application of a transverse force thereby to deflect the stock and to increase the tension therein;.

measuring the transverse force required to deflect said stock through the use of a tensiometer which measured force is predictably related to the said normal tension when said stock is undeflected;

adjusting the speeds of the rolls in adjacent stands while said stock is deflected to produce the desired normal tension in this section of the moving stock;

then removing said transverse deflecting force and allowing the stock to resume its normal undeflected condition;

thereafter periodically deflecting said moving stock section transversely through said standard fixed distance and noting the force required to cause said deflection;

adjusting the speeds of the rolls of said adjacent stands to change the said stock deflecting force to that which is predictably related to the said normal tension in the undeflected stock; and

then removing said deflecting force and allowing said stock to resume its normal undeflected condition.

2. The method set forth in claim 1, said adjusting of the speeds of said rolls being controlled by manual operation.

3. The method set forth in claim 1, said adjusting of the speeds of said rolls being controlled by automated devices the extent of whose movement is related to the said then existing transverse force.

4. In a rolling mill having a plurality of roll stands and means for varying the speed of the work rolls in said roll stands, apparatus for determining the tension present in the product being rolled as it is passing from one stand to the next, comprising: a product engaging element located between said stands; support means for carrying said product engaging element for movement in a direction transverse to the path traveled by the product passing between said stand; operating means associated with said support means for moving the product engaging element a predetermined constant distance whereby said element will engage the product and move the engaged part of the product a uniform transverse distance in relation to its normal path of travel between said roll stands and whereby the product will press against said element with a force which is predictably related to the undeflected product tension; a load cell included as part of said support means and located between said product engaging element and said operating means; and, means actuated by said load cell for indicating said force.

5. The apparatus as claimed in claim 4 wherein said support means is comprised of a bell crank pivotally mounted for movement about an axis spaced laterally from and extending in a direction transverse to the path traveled by the product passing between the roll stands, said product engaging element being mounted on one arm of the crank, and said load cell being pivotally attached at opposite ends respectively to the other of said crank and said operating means.

6. The apparatus as claimed in claim 5 wherein said product engaging element comprises a roller, and

wherein said operating means comprises a fluid operated piston-cylinder assembly.

said stock through the use of a tensiorneter which measured force is predictably related to the stock tension when the stock is undeflected;

adjusting the speeds of the rolls in the adjacent roll stands while said stock is deflected to achieve a measured force which is predictably related to the desired predetermined normal tension;

then removing said transverse deflecting force and allowing the stock to resume its normal undev t'lected condition. 

1. The method of adjusting the tension of moving stock being rolled in a rolling mill to a predetermined normal tension between each pair of adjacent stands comprising the steps of: transversely moving the stock at a position intermediate the said adjacent roll stands a standard fixed distance by the application of a transverse force thereby to deflect the stock and to increase the tension therein; measuring the transverse force required to deflect said stock through the use of a tensiometer which measured force is predictably related to the said normal tension when said stock is undeflected; adjusting the speeds of the rolls in adjacent stands while said stock is deflected to produce the desired normal tension in this section of the moving stock; then removing said transverse deflecting force and allowing the stock to resume its normal undeflected condition; thereafter periodically deflecting said moving stock section transversely through said standard fixed distance and noting the force required to cause said deflection; adjusting the speeds of the rolls of said adjacent stands to change the said stock deflecting force to that which is predictably related to the said normal tension in the undeflected stock; and then removing said deflecting force and allowing said stock to resume its normal undeflected condition.
 2. The method set forth in claim 1, said adjusting of the speeds of said rolls being controlled by manual operation.
 3. The method set forth in claim 1, said adjusting of the speeds of said rolls being controlled by automated devices the extent of whose movement is related to the said then existing transverse force.
 4. In a rolling mill having a plurality of roll stands and means for varying the speed of the work rolls in said roll stands, apparatuS for determining the tension present in the product being rolled as it is passing from one stand to the next, comprising: a product engaging element located between said stands; support means for carrying said product engaging element for movement in a direction transverse to the path traveled by the product passing between said stand; operating means associated with said support means for moving the product engaging element a predetermined constant distance whereby said element will engage the product and move the engaged part of the product a uniform transverse distance in relation to its normal path of travel between said roll stands and whereby the product will press against said element with a force which is predictably related to the undeflected product tension; a load cell included as part of said support means and located between said product engaging element and said operating means; and, means actuated by said load cell for indicating said force.
 5. The apparatus as claimed in claim 4 wherein said support means is comprised of a bell crank pivotally mounted for movement about an axis spaced laterally from and extending in a direction transverse to the path traveled by the product passing between the roll stands, said product engaging element being mounted on one arm of the crank, and said load cell being pivotally attached at opposite ends respectively to the other of said crank and said operating means.
 6. The apparatus as claimed in claim 5 wherein said product engaging element comprises a roller, and wherein said operating means comprises a fluid operated piston-cylinder assembly.
 7. The method of adjusting the tension of moving stock being rolled in a rolling mill to a predetermined normal tension between each pair of adjacent roll stands comprising the steps of: transversely moving the stock at a position intermediate the said adjacent roll stands a standard fixed distance by the application of a transverse force to thereby deflect the stock and to increase the tension therein; measuring the transverse force required to deflect said stock through the use of a tensiometer which measured force is predictably related to the stock tension when the stock is undeflected; adjusting the speeds of the rolls in the adjacent roll stands while said stock is deflected to achieve a measured force which is predictably related to the desired predetermined normal tension; then removing said transverse deflecting force and allowing the stock to resume its normal undeflected condition. 